<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <canvas id="myCanvas"> 你的浏览器不支持 html5 </canvas>
    <script>
      //画布
      var c = document.getElementById('myCanvas')
      //画笔
      var ctx = c.getContext('2d')
      //画矩形
      ctx.rect(20, 20, 150, 100)
      ctx.stroke()
    </script>
  </body>
</html>
